How can I simplify this redundant code?

Can someone please help me simpling this redundant piece of code?

if (isset($to) === true)
{
    if (is_string($to) === true)
    {
        $to = explode(',', $to);
    }

    $to = array_filter(filter_var_array(preg_replace('~[<>]|%0[ab]|[[:cntrl:]]~i', '', $to), FILTER_VALIDATE_EMAIL));
}

if (isset($cc) === true)
{
    if (is_string($cc) === true)
    {
        $cc = explode(',', $cc);
    }

    $cc = array_filter(filter_var_array(preg_replace('~[<>]|%0[ab]|[[:cntrl:]]~i', ''开发者_如何学运维, $cc), FILTER_VALIDATE_EMAIL));
}

if (isset($bcc) === true)
{
    if (is_string($bcc) === true)
    {
        $bcc = explode(',', $bcc);
    }

    $bcc = array_filter(filter_var_array(preg_replace('~[<>]|%0[ab]|[[:cntrl:]]~i', '', $bcc), FILTER_VALIDATE_EMAIL));
}

if (isset($from) === true)
{
    if (is_string($from) === true)
    {
        $from = explode(',', $from);
    }

    $from = array_filter(filter_var_array(preg_replace('~[<>]|%0[ab]|[[:cntrl:]]~i', '', $from), FILTER_VALIDATE_EMAIL));
}

I tried using variable variables but without success (it's been a long time since I've used them).

Variable variables:

$vars = array('to', 'cc', 'bcc', 'from');
foreach ($vars as $varname) {
    if (isset($$varname)) {
        if (is_string($$varname)) {
            $$varname = explode(',', $$varname);
        }
        $$varname = array_filter(filter_var_array(preg_replace('~[<>]|%0[ab]|[[:cntrl:]]~i', '', $$varname), FILTER_VALIDATE_EMAIL));
    }
}

Regular (Without using variable variables):

$vars = compact('to', 'cc', 'bcc', 'from'); 
foreach ($vars as $name => &$var) {
    if (is_string($var)) {
        $var = explode(',', $var);
    }
    $var = array_filter(filter_var_array(preg_replace('~[<>]|%0[ab]|[[:cntrl:]]~i', '', $var), FILTER_VALIDATE_EMAIL));
}
extract ($vars);

Note, you don't need isset, because compact will only import variables that are set. All others are ignored...

BTW: You don't need the === true. isset() or is_string() will always return a boolean. So the === true is redundant...

You could do (untested)

$vars = array($from, $to, $cc, $bcc);

foreach ($vars as $var)
        {
        $var = explode(',', $var);
        ....
        ...
        }

$from = $vars[0];
$to = $vars[1];
$cc = $vars[2];
$bcc = $vars[3];

Put it in a function?

function validate($str) {
    if (isset($str) === true)
    {
        if (is_string($str) === true)
        {
            $str = explode(',', $str);
        }

        $str = array_filter(filter_var_array(preg_replace('~[<>]|%0[ab]|[[:cntrl:]]~i', '', $str), FILTER_VALIDATE_EMAIL));
    }
    return $str;
}

$to = validate($to);
$cc = validate($cc);
$bcc = validate($bcc);
$from = validate($from);

Even without going the full variable variables route, you could simplify this a lot just by putting the checks into a common function, and then doing:

$to = cleanup_email_addrs($to);
$cc = cleanup_email_addrs($cc);
$bcc = cleanup_email_addrs($bcc);
$from = cleanup_email_addrs($from);

Just stick the values in an array and iterate over it.

function cleanEmails($value) {
    if (is_string($value)) {
        $value = explode(',', $value);
    }
    return array_filter(filter_var_array(preg_replace('~[<>]|%0[ab]|[[:cntrl:]]~i', '', $value), FILTER_VALIDATE_EMAIL));
}

$fields = array();
if (isset($to)) {
    $fields['to'] = $to;
}
if (isset($from)) {
    $fields['from'] = $from;
}
if (isset($cc)) {
    $fields['cc'] = $cc;
}
if (isset($bcc)) {
    $fields['bcc'] = $bcc;
}
$result = array_map('cleanEmails', $fields);

The end result will be a 2 dimensional array, first index will be the fields that were set, second index will be the respective email addresses...

I could do this:

You can probably create a function for that:

function checkIt($var)
{
    if (isset($var) === true)
    {
        if (is_string($var) === true)
        {
          $var = explode(',', $var);
        }

        $to = explode(',', $var);
        $to = array_filter(filter_var_array(preg_replace('~[<>]|%0[ab]|[[:cntrl:]]~i', '', $to), FILTER_VALIDATE_EMAIL));
    }

    return $to;
}

And now you can pass your variables to this function.

For starters you can get rid of the isset() === true; isset() returns either true or false.

And of course put it in a function as all your if statements seem to do the same thing, but that´s been mentioned before...

By the way, does your array_filter line work if the input is not an array()?

If not, you need to include that statement inside the if (is_string()) statement.